Last month I wrote reverently
about the history of nautical charts and not so reverently about certain
bits of monkey business we’re experiencing as they transition from
paper to electronic form. Too many formats, too much incompatibility,
royalty wars—times of change can be messy. But, in this month’s
continuation of the discussion, I bring you mostly good news.

Let’s start with
NOAA’s misunderstood but radical Electronic Navigation Chart (ENC)
project. ENCs are the beginning of a true vector chart system, a concept
that needs explaining. I’ll use the San Francisco ENC above for visual
reference. It covers some of the same area as shown last month with an
1853 paper chart (a bit of which is overlaid). Only instead of being hand-drawn
by a skilled and artistic cartographer, probably wearing a starched collar
and a green eyeshade, the ENC was drawn by a computer.

Never mind for now how
much more elegant the 1853 chart looks and how it actually appears more
detailed, even though the creators lacked even motorboats for their work,
let alone GPS, depthsounders, or graphic workstations. Compared to the
paper system, ENC vector technology is an entirely different animal, and
one just beginning its evolution. An ENC is not even a drawing. If you
translated the file into our alphabet, which is possible, you’d find
thousands of tightly coded lines similar to this: “L4-102, 37.809439,
122.427391, Y2.5,...” It might reference a library file containing
the symbol for that light buoy at upper left on the ENC (and in data box
below), along with its lat/lon and unique details. It’s a record
in a database, and the software that “draws” it onto the screen
can do so in very flexible ways. If you want the lights to disappear or
show in an alternate symbol set, no problem, just check some boxes with
your mouse. By contrast, a raster file is just a stubborn list of pixel
locations and colors, like a digital photograph.

But you may already
understand this, as the vector charts produced by C-Map, Garmin, Transas,
etc. share the same characteristics. Several things set ENCs apart. For
one, they are official government cartography. In fact, since they’re
based on the International Maritime Organization’s S57 standard,
they are official international vector charts. More significant is that
ENCs will eventually become NOAA’s base technology, tentatively the
world’s. Even though the first set is being made mostly by tracing
the existing raster charts, in due time the data will remain real data,
not pixels, from start to finish. For instance, some of the current ENCs
use original Corps of Engineers channel dredging records and Coast Guard
buoy locations instead of the less accurate representations that were
drawn into the limited- scale paper system.

That’s what I mean
by true vector technology, and it makes so much sense compared to the
current situation. Contemplate the silliness of surveyors sending GPS
numbers describing a coastline into the home office where the data becomes
curves on a raster file to which the vector vendors arduously apply special
tracing software in order to turn it back into numbers! Realize that when
the Coast Guard moves a buoy in an all-vector system, the tiny change
record can be e-mailed into NOAA and out to vessels—zing, zing—where
the relevant chart is instantly updated.

There’s more. You
might hear around the chart shops that ENC coverage is meant mainly for
ships and will not include all the current paper detail, but NOAA electronic
chart products manager Mike Brown says it isn’t so. While he can’t
cite a completion date, he says that ENCs will in due time duplicate the
entire U.S. paper portfolio and then replace it. And NOAA is giving them
all away. Dozens of “cells”—the charts are organized in
multiscaled regions instead of familiar paper sizes, another sign of the
future—are available for downloading right now at chartmaker.noaa.gov.
Several free viewing programs are available on the Web, and charting programs
Fugawi and MaxSea can plot on ENCs; others like The Cap’n will follow
soon.